This invention relates to a dehydration apparatus in which particulate material is carried by a fluid medium through a rotary dryer.
Particulate matter which includes moisture or the other gaseous material may be passed through a rotary dryer for removal of the liquid or gaseous medium with subsequent separation of the particles from the fluid medium. Generally, in a rotary dryer system which is widely employed in industry and agricultural product drying and the like includes a gas or oil fired furnace or other heat source mounted to one end of a horizontally located and supported rotary dryer to supply hot air which is mixed with the product and through which particulate laden air is passed. The dryer includes a plurality of concentric cylinders or drums defining a central inlet passageway connected at one end to the hot air and connected in series by one or more intermediate passageways to an outermost discharge passageway. The particulate laden air moves through the multiple passageways by suction created by a dryer discharge fan. The rotary cylinders include suitable surface vanes to continuously circulate the particulate matter within the drums to the top portion and establish intimate mixing of the particles with the hot air or gases from the heat source. The air with the dried particle is fed to one or more cyclone separators, drop-out boxes or other suitable means for the separation of the dust particles from the hot gases. A cyclone separator generally includes a large vertically oriented unit having a top cylindrical inlet portion with a conical bottom discharge portion as well as a central top air exhaust duct member. The particulate laden air is fed into the unit with a centrifugal motion such as that as it moves downwardly through the cylindrical portion the particles are concentrated in the outer layer, and continue to drop downwardly through the cone-shape portion for exiting from the bottom. The primary carrier air is drawn upwardly through the center duct to the top of the cyclonic separator for further treatment or exhausting. For example, the air may be recirculated to the furnace. Alternately, a series of cyclonic separators may be provided to further clean the carrier air if it is to be exhausted to the atmosphere. Such rotary dryers are widely employed in connection with many industrial and agricultural products. Generally appropriate housing of the system apparatus includes enclosure of the furnace and dryer with the cyclonic separator mounted on or in a support structure.
Such systems are well known and are furnished by various sources of manufacture. Generally, the prior art has followed a basic pattern for years in which three constant diameter concentric cylinders are interconnected to define a triple pass drying flow path.
Although they provide satisfactory results, they do not provide necessarily the proper degree of drying which is often desired and/or required. Further, in various application scorching or excessive drying of particulate may occur. This is known to be particularly troublesome in connection with certain high sugar content wood products where scorching occurs as well as products or the like where various sized particles are encountered and degradation of product quality may occur if proper drying is not provided. Although various systems have been suggested a totally acceptable solution has not been found prior to the present invention.